Add mixer for FI32 and S16N

Audio volume should now work on !HAVE_FPU. This is untested though.

modules/LIST

@@ -118,6 +118,7 @@ $Id$
  * fb: video output module for the Linux framebuffer
  * fbosd: framebuffer osd plugin
  * filesystem: Filesystem access module
+ * fixed32_mixer: Fixed-point audio mixer
  * flac: Flac decoder using libflac
  * flacsys: FLAC demuxer
  * float32_mixer: Precise float32 audio mixer

modules/audio_mixer/Modules.am

 SOURCES_trivial_mixer = trivial.c
 SOURCES_float32_mixer = float32.c
+SOURCES_fixed32_mixer = fixed32.c
 
 libvlc_LTLIBRARIES += \
 	libfloat32_mixer_plugin.la \
+	libfixed32_mixer_plugin.la \
 	libtrivial_mixer_plugin.la

modules/audio_mixer/fixed32.c

+/*****************************************************************************
+ * fixed32.c : fixed-point software volume
+ *****************************************************************************
+ * Copyright (C) 2011 Rémi Denis-Courmnot
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <vlc_common.h>
+#include <vlc_plugin.h>
+#include <vlc_aout.h>
+#include <vlc_aout_mixer.h>
+
+static int Activate (vlc_object_t *);
+
+vlc_module_begin ()
+    set_category (CAT_AUDIO)
+    set_subcategory (SUBCAT_AUDIO_MISC)
+    set_description (N_("Fixed-point audio mixer"))
+    set_capability ("audio mixer", 9)
+    set_callbacks (Activate, NULL)
+vlc_module_end ()
+
+static void FilterFI32 (aout_mixer_t *, block_t *, float);
+static void FilterS16N (aout_mixer_t *, block_t *, float);
+
+static int Activate (vlc_object_t *obj)
+{
+    aout_mixer_t *mixer = (aout_mixer_t *)obj;
+
+    switch (mixer->fmt.i_format)
+    {
+        case VLC_CODEC_FI32:
+            mixer->mix = FilterFI32;
+            break;
+        case VLC_CODEC_S16N:
+            mixer->mix = FilterS16N;
+            break;
+        default:
+            return -1;
+    }
+    return 0;
+}
+
+static void FilterFI32 (aout_mixer_t *mixer, block_t *block, float volume)
+{
+    const int64_t mult = volume * mixer->input->multiplier * FIXED32_ONE;
+
+    if (mult == FIXED32_ONE)
+        return;
+
+    int32_t *p = (int32_t *)block->p_buffer;
+
+    for (size_t n = block->i_buffer / sizeof (*p); n > 0; n--)
+    {
+        *p = (*p * mult) >> 33; // FIXED32_FRACBITS;
+        p++;
+    }
+}
+
+static void FilterS16N (aout_mixer_t *mixer, block_t *block, float volume)
+{
+    const int32_t mult = volume * mixer->input->multiplier * 0x10000;
+
+    if (mult == 0x10000)
+        return;
+
+    int16_t *p = (int16_t *)block->p_buffer;
+
+    for (size_t n = block->i_buffer / sizeof (*p); n > 0; n--)
+    {
+        *p = (*p * mult) >> 16;
+        p++;
+    }
+}